We have the same goal weight. How tall are you? I'm 5'6".
It sounds like you have at least one really good motivation to lose weight, but you have to realize that if you don't want to gain back lost weight over and over then you need to make this a lifestyle change. You need to change your eating and exercise habits for the better for the long-term, rather than just until you get down to 115. That's why you need to pick a nutrition/exercise program that will work for you throughout life.
My advice is to read as much as you can on nutrition and exercise in the next few weeks. Learn how to nourish your body through eating right and exercising. Portion control, veggies, fruits, whole grains, fiber, lean protein, good fats (like ev olive oil, salmon, avocados, etc.) are all very important in your diet and will help you to reach your goal.
One last thing. You said that you want to be a model for the rest of your life, but most models careers end in their 30's (maybe 40's). You should follow your dream, but you should also learn how to do something else, if not to make a living then for your own personal growth.
Good luck! And
to 3fc! You'll love it here!